Growth rate and composition of directionally solidified intermetallic TiAl–Nb alloys with different solidification conditions  

作　　者：Li-Wei Zhang Jun-Pin Lin Xiang-Jun Xu Jian-Ping He Xian-Fei Ding Xiao-Ou Jin 

机构地区：[1]State Key Laboratory for Advanced Metals and Materials,University of Science and Technology Beijing [2]Materials and Chemistry School,Zhongyuan University of Technology [3]National Center for Materials Service Safety,University of Science and Technology Beijing [4]School of Architecture and Engineering,Heilongjiang University

出　　处：《Rare Metals》2016年第1期54-64,共11页稀有金属（英文版）

基　　金：financially supported by the National Natural Science Foundation of China(Nos.51271016 and U1204508);the National Basic Research Program of China(No.2011CB605500);the Doctoral Program of Higher Education of China(No.20120006120042);the Fundamental Research Funds for the Central Universities(No.FRF-TP-14-062A2)

摘　　要：Intermetallic Ti-xAl-8Nb（x = 41,43,45,47,49;at%） alloys were solidified unidirectionally upwards with a constant temperature gradient of G=3.8 K·mm^（-1）at wide range of growth rates of v=10-400 μm·s^（-1）using a Bridgman directional solidification（DS） furnace.Microstructural parameters including the primary dendrite arm spacing（λ_1）,secondary dendrite arm spacing（λ_2）,dendrite tip radius（R） and mushy zone depth（d） were measured statistically.The values of λ_1,λ_2,R and d decrease as the growth rate increases for a given composition（x）.The values of λ_1,λ_2,R and v increase with the increase in x value,while the value of d firstly increases and then decreases with the increase in x value for a given v.The relationships between λ_1,λ_2 and R were analyzed by the linear regression.The average growth rate exponent of λ_1 is 0.29,which is in accordance with the previous experimental observations,and that of λ_2 is close to the previous experimental results,while those of R and d are lower than the results in other alloy systems.In addition,theoretical models for λ_1,λ_2 and R were compared with the experimental observations,and a comparison of the present experimental results with the theoretical models and previous experimental results was also made.Intermetallic Ti-xAl-8Nb（x = 41,43,45,47,49;at%） alloys were solidified unidirectionally upwards with a constant temperature gradient of G=3.8 K·mm^（-1）at wide range of growth rates of v=10-400 μm·s^（-1）using a Bridgman directional solidification（DS） furnace.Microstructural parameters including the primary dendrite arm spacing（λ_1）,secondary dendrite arm spacing（λ_2）,dendrite tip radius（R） and mushy zone depth（d） were measured statistically.The values of λ_1,λ_2,R and d decrease as the growth rate increases for a given composition（x）.The values of λ_1,λ_2,R and v increase with the increase in x value,while the value of d firstly increases and then decreases with the increase in x value for a given v.The relationships between λ_1,λ_2 and R were analyzed by the linear regression.The average growth rate exponent of λ_1 is 0.29,which is in accordance with the previous experimental observations,and that of λ_2 is close to the previous experimental results,while those of R and d are lower than the results in other alloy systems.In addition,theoretical models for λ_1,λ_2 and R were compared with the experimental observations,and a comparison of the present experimental results with the theoretical models and previous experimental results was also made.

关 键 词：TiAl-Nb alloys INTERMETALLIC Directionalsolidification Microstructural parameters Soluteconcentration 

分 类 号：TG146.23[一般工业技术—材料科学与工程]